High-performance propeller

ABSTRACT

A high-performance propeller has one hub and a plurality of blades, characterized in that a double-side or a single-side arc brim is provided at the tip of each blade. The propeller of the invention can provide a small induced drag and convert the centrifugal force to the effective force so as is to increase the differential pressure near the tip of blades and thereby increase the acting force on blades. Under the condition of same power consumption, it has been tested for the large propeller in the type of lateral inclination that the amount of flow is increased about 12%˜17%, which is equivalent to save energy 40%˜70%. Since the fluid dynamic performance presents the aspect ratio approaching infinity, the width of the blades can be increased whereas the induced drag is not increased. Applying the method of increasing the area of the blades and decreasing the velocity of outflow fluid, the effect on saving of energy can be further improved greatly on the present basis.

TECHNICAL FIELD

[0001] The invention relates to a propeller, particularly to a propellerwith the blades provided with double-side or single-side arc brims atthe tips thereof.

BACKGROUND ART

[0002] For the blades of the propeller in the art, due to the effect ofinduced drag the maximum pressure point is located at the place of about0.7 of blade length where is the main operational region. The movementvelocity of blades arrives to maximum in the region from the place of0.7 blade length to the tip of blade, which region occupies about halfof entire rotational area of propeller and should produce about 70%acting force in terms to the calculation of the deserved acting force.For the conventional propeller, the differential pressure between thepositive-pressure face and the negative-pressure face in this regiondecreases instead and almost to zero at the tip of blade. The tip ofblade is located at the position of maximum movement velocity of blades,but also the position of maximum loss of energy in conventionalpropeller. There are no stable boundaries between the positive-pressureface and the negative-pressure face of the blade of propeller in the artand between these pressure faces and surrounding medium, thereby theloss of energy at the tip of blade is serious. Presently there is adesign in which a brim is added to the blade with relatively big aspectratio, but the beneficial result of saving energy is not obvious. Thisis because the induced drag of blade itself is relatively smaller, theblade span is longer arm of force is long, and thereby the moment is bigso as to deform the blade easily, which is easy to cause great form dragby the brim. Presently the design in which the blade is provided with abrim, or the design in which the propeller has a outer ring in the shapeof tunnel, and or the application of propeller in the tunnel havebasically not considered the influence of the brim or tunnel on radialsupplement of fluid. The shape and size of the brim not giveconsideration to both the elimination of induced drag and the increaseof radial supplement of fluid. The brim or tunnel influences thesupplement of fluid and thereby reduces the amount of fluid acting onpropeller, so that the effective acting force produced by the propelleris decreased and consequently the efficiency of propeller drops.

DISCLOSURE OF THE INVENTION

[0003] The objective of the invention is to provide a high-performancepropeller, which can overcome the disadvantages of the propeller in theart as described above.

[0004] The propeller according to the invention has one hub and aplurality of blades, characterized in that a double-side or asingle-side arc brim is provided at the tip of each blade.

[0005] The propeller of the invention can change the flow condition andthe pressure distribution near the tip of blade by means of thedouble-side or single-side arc brims. Therefore the fluid dynamicperformance of the propeller of the invention presents the aspect ratioapproaching infinity and the small induced drag. The centrifugal forceof fluid can be converted to the effective acting force so as toincrease the acting force near the tip of blade, whereas there almost noform drag in rotational direction is produced by the double-side orsingle-side arc brim. Under the condition of almost no induced drag, thebeneficial result of reducing loss of energy is obvious by means oflengthening the chord of blade, thereby increasing the area of blade anddecreasing the velocity of outward flow of fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The invention will be further described with reference toaccompanying drawings and embodiments as follows.

[0007]FIG. 1 is a schematic view of the propeller construction anddouble-side arc brims of the blade according to the invention.

[0008]FIG. 2 is a schematic view of the propeller construction ofdouble-side arc brims of the blades with a strengthening ring accordingto the invention.

[0009]FIG. 3 is a schematic view of a single-side arc brim with outwardinclination and an anti-overflow edge.

[0010]FIG. 4 is a schematic view showing the position of avortex-generated zone.

[0011]FIG. 5 is a schematic developed view showing the tips ofsingle-side arc brims of blades of propeller with a strengthening ringaccording to the invention.

BEST MODE OF EMBODIMENTS OF THE INVENTION

[0012] The terms of ‘double-side arc brim and single-side arc brim ofblade’ is hereafter referred to as simply ‘brim’ for the purpose ofclarification.

[0013] Embodiment 1 High-performance propeller in the type of propellingused in air

[0014] Referring to FIGS. 1 and 2, the propeller for this embodiment hasa hub 2 and twelve blades 3, characterized in that a double-side arcbrim 1 is affixed at the tip of blade 3. A strengthening ring 4 isdisposed among the blades. The propeller may be made of any suitablematerial such as plastic, metal by moulding, welding and othermechanical ways.

[0015] For the propeller of this embodiment, the diameter of thepropeller is 0.8 m, the effective angle of attack is 14 deg., the liftcoefficient L is taken as 1, the aspect ratio is 4, the area of blade isequal to rotational area of propeller, the height of brim is equal to26% chord length of blade and the brim has a 22 deg. outwardinclination. The strengthening ring 4, is located at the tip of theblades and beyond the axial width of blades. The strengthening ring andbrim are connected by connecting strips which plane is substantiallyparallel to the rotational plane of propeller or at an angle to the flowdirection so as to produces no acting force but friction drag only.

[0016] The static thrust F that can be produced theoretically accordingto the propeller of the invention is calculated in terms of thetechnical target of 550 m/s of velocity at the tip of blade, notconsidering the effect of compressibility of air.

[0017] F—thrust, kgf A—area of the blade, 0.5 m²

[0018] r—rotational velocity, 219 rps V_((m))—velocity at the tip ofblade, 500 m/s

[0019] L—lift coefficient, 1

[0020] ρ—air density, 0.125 kg.s²m⁴ R—radius, 0.4 m

thrust F=0.25 Lρ A V ² _((m))=4726 kgf=46320 N

[0021] Calculation of the friction drag Z produced by the brims andstrengthening ring:

[0022] Comparing with the conventional propeller, the friction dragproduced by brims and strengthening ring is added by the propeller ofthe invention, thus the friction drag Z produced by brims andstrengthening ring and the its ratio to thrust are calculated as followsso as to asses its effect.

[0023] The friction drag Z produced by brims and strengthening ring iscalculated employing the calculation formula for drag of plate. Assumingthe shape of brims and strengthening ring only cause the friction dragand the drag is approximate to that of plate, the friction drag iscalculated according to the area of brims and strengthening ring whichis equal to 50% rotational area at the tip of blade of propeller.

[0024] Z—friction drag produced by brims and strengthening ring, kgf

[0025] R—Reynolds number

[0026] M—surface area of brims and strengthening ring, 0.125 m²

[0027] C—drag coefficient V_((m))—linear velocity of brim, 550 m/s

[0028] ρ—air density, 0.125 kg.s²/m⁴

[0029] γ—viscosity coefficient of air, 1.45×0.00001 m²/s

R=(2.5×550)÷(1.45×0.00001)=94827586

C=0.455÷(LgR)^(2.58)=0.0021

Z=0.5 C ρ M V ² _((m))=0.5×0.0021×0.125×0.125×550×550=4.9625 kgf

[0030] The ratio of the friction drag produced by brim and strengtheningring to the thrust is calculated as follows:

drag/thrust=4.9625÷4726=0.00105

[0031] Therefore, the effect of the friction drag produced by brims andstrengthening ring on the propeller of the invention is insignificant.

[0032] Comparison of induced drag loss for the propeller of theinvention with that for the conventional propeller is:

[0033] 1. Calculation of the amount of induced drag loss for thepropeller of the invention: A - area of propeller, 0.5 m λ - aspectratio ≈ ∞ V_((m)) - velocity at the tip of blade, 550 m/s L - liftcoefficient, 1

[0034] The induced drag coefficient C_(I) is evaluated as:

C _(I) =L ^(2/)(πλ)=1/(π∞)≈0

[0035] The induced drag R_(I) is evaluated as:

R _(I)=0.5 C _(I) ρA V ² _((m))=0

[0036] 2. Calculation of the amount of induced drag loss for theconventional propeller: A - area of propeller, 0.5 m λ - aspect ratio, 4V_((m)) - velocity at the tip of blade, 550 m/s L - lift coeffient, 1

[0037] The induced drag coefficient C_(I) is evaluated as:

C _(I) =L ²/(πλ)=1/12.6=0.0796

[0038] The induced drag R_(I) is evaluated as:

R _(I)=0.5 C _(I) ρA V ² _((m))=752 kgf

[0039] The ratio of induced drag to thrust for the propeller of theinvention: 0/4726=0

[0040] The ratio of induced drag to thrust for the conventionalpropeller: 752/4726=0.13

[0041] Under this condition, the induced drag loss can be reduced anamount equivalent to 13% thrust for the propeller of the invention.

[0042] Embodiment 2. High-performance propeller in the type ofpropelling with blades having excessively wide chord

[0043] The propeller for this embodiment has a hub 2 and six blades 3,characterized in that a double-side arc brim 1 is affixed at the tip ofeach blade 3. For the propeller of this embodiment, the diameter is 0.8m, the axial length is 0.92 m, the angle of attack on the inflow side ofblade is 60 deg, the angle of attack on the outflow side of blade is 30deg. and the aspect ratio is 0.4. The propeller is configured in ahelical form in its entirety. The height of brim on thenegative-pressure face of blade is 0.03 m. The height of brim on thepositive-pressure face of blade is 0.03 m for the inflow side and is0.08 m for the outflow side. The brim has no any outward inclination.The anti-overflow edge is 0.06 m wide and at a 60 deg. angle to thebrim.

[0044] Now the propeller of the invention will be compared with that inthe turbo-fan engine or compressor having same sucking port area andunder same operational condition. The propeller of the invention ischaracterized in that the fluid can be sucked radially so as to increasethe sucking amount of fluid greatly and thus increase the amount offluid acting on blades. The sucked air on the negative-pressure face ofblade will enter the space constituted by the positive-pressure face ofblade and the brim as well as the anti-overflow edge so as to be guidedand restricted because the positive-pressure face of blade is providedwith the brim and the anti-overflow edge. In the course of pressuretransition from the negative-pressure face of a blade to thepositive-pressure face of next adjacent blade, the interference betweenthe positive and negative-pressure faces of blade can be reduced, andthereby the differential pressure can be increased through the fluidguided in the space between the positive and negative-pressure faces ofblade. The flux of fluid for the propeller of the invention is so bigthat it is capable of converting the centrifugal force to the effectiveacting force. The effective acting force is increased and the losses ofdrag and other secondary flow are decreased so as not to be easy togenerate panting and flutter of the blades.

[0045] m—amount of fluid sucked on the side facing wind for thepropeller

[0046] v—velocity of outward flow of fluid

[0047] M—amount of radial fluid sucked at the tip of blade for thepropeller of the invention

[0048] F—thrust of the propeller

[0049] The thrust produced in machine in the type of thrust jet dependsmainly on the change of fluid momentum.

[0050] The thrust F produced in the conventional thrust fan is:

F=d(mv)/dt

[0051] Assuming that the amount of fluid sucked on the side facing windfor the propeller of the invention (m) is same as that of the fan withsame area facing wind, thus the total amount of flow is (m+M) forpropeller of the invention because of supplied radial sucking amount M.Assuming that the velocity of outward flow of fluid (v) is same as (infact, is larger than) that for the conventional propeller, thus thethrust F produced in the propeller of this embodiment is:

F=d[(m+V)v]/dt

[0052] Therefore, the thrust produced in the propeller of the inventionis larger than that of the conventional fan, such as the fan of theturbo-fan engine with same area facing wind; and the amount sucked islarger than that of jet-engine compressor with same area facing wind.Moreover, the thrust, thrust-weight ratio and efficiency for the enginewill increase greatly because of the increased flux of fluid. Thepropeller of this embodiment is also adapted to used for axial flowpump, smoke exhauster and so on.

[0053] Embodiment 3 High-performance propeller for the conventional fan

[0054] This embodiment is compared with the conventional fan with 400 mmdiameter. The construction, shape, size and angle of attack for thepropeller of the invention is same as those of the conventional fanexcept that the blade is provided with single-side arc brim 5, as shownis FIGS. 3, 4 and 5.

[0055] The propeller for this embodiment has a hub 2 and four blades 3,characterized in that a single-side arc brim 5 is affixed at the tip ofeach blade 3. The width of brim is 40 mm, brim has 15 deg. outwardinclination, and the equivalent diameter of fan is 420 mm. The junctureand its nearby region between the brim and the tip of negative-pressureface of blade is in the shape of non-streamline arc on which there is a6 mm wide vortex-generated zone 7 as shown in FIG. 3 and FIG. 4.

[0056] The equivalent diameter of fan of this embodiment is 420 mm.Under the condition of same rotational velocity, the drag is equivalentto that of the 400 mm conventional fan, the power is equivalent to thatof the 400 mm conventional fan, and the amount of wind produced islarger than that of 420 mm fan.

[0057] Presently the testing has proved that under the condition ofconstant motor power and energy consumption, the propeller of theinvention increases the amount of wind about 12%˜17%, which isequivalent to save energy about 40˜70% in terms of the cubicrelationship between the amount of wind and consumption power.

[0058] Each part of brim of the propeller of the invention issubstantially concentric with the propeller. The parts of brim, whichserve the same function, project axially on the roughly same radius ofrevolution. In principle only the friction drag is required to beproduced in rotational direction from the brims. If the brim has aninclination, it will produce the form drag, which can increases ordecreases the form force from the pressure at the tip of blade. Asrequired, the brim can develop suitably in the rotational direction ofthe blade into the form of an approximate involute so as to change thesucked amount of fluid and thereby the result of blade action.

[0059] The propeller of the invention is not very sensitive to thechange of the inclination of the brim in a certain extent, thus can beused as a propeller with variable pitch. The propeller can be alsodesigned as one with brims in special shape so as to meet the needs invarious operational conditions and the requirement in aesthetics.

[0060] The invention involves a new design conception and a novel designideology. In past, it may be not noticed that the radial supplement offluid at the tip of blade of the propeller can affect the operationalcondition of propeller. Therefore, no systematic guiding ideology anddesign conception can be found when the propeller with brims or thepropeller within a tunnel is employed, thus it seems to be carried outvery blindly. Our experiments and testing have proved that the design ofimproper brims of blades or application of the conventional propellerwithin a tunnel will reduce the amount of fluid acting on blades,decrease thrust of propeller or conveying amount of fluid, and therebydecrease the efficiency of propeller. Therefore, the design of the brimsfor the propeller of the invention should consider that the action ofbrims would decrease both the induced drag and fluid supplement. Thereasonable control of the radial fluid flow at the tip of blade cangreatly increase the thrust of propeller, the conveying amount of fluidand consequently the efficiency of the propeller. The invention followsthe systematic design ideology. The action of brims is utilized todecrease the induced drag. Thus under the condition of almost no induceddrag, the aspect ratio is decreased, the deformation of blade isdecreased, the effective area of blade is increased, the outflowvelocity of fluid is decreased, and the efficiency of propeller is alsoimproved greatly according to the theoretical evaluation. Presently thesaved energy (40%˜70%) is obtained mainly by the decrease of induceddrag.

[0061] It is found in experiments that under a certain conditions, thetunnel will give effect to decrease the flux of fluid for the propelleror fan. The propeller of the invention can eliminate this unfavorableeffect, and also give favorable effects to cause the tunnel to maintainthe pressure and reduce the leakage at tip of blades. The suitable fitof propeller of the invention within the tunnel will greatly improve theeffectiveness for conveying the fluid and compressing the air. Thepropeller of the invention is generally not used within the tunnel inthe form of close fit. The propeller should be disposed at the both endsof the tunnel with the outflow or inflow side thereof suitably fitted toone of the ends of the tunnel. The relatively suitable application ofthe propeller of the invention is in such way that when the fluid ispressed into tunnel, the most part of the propeller is beyond the tunneland only outflow side thereof interfaces the tunnel; and when the fluidis sucked out the tunnel, the most part of the propeller is within thetunnel and only outflow side thereof faces outward. The tunnel isrequired to leave space for radial supplement of fluid to the propeller.

[0062] The shape, size, spatial angle and spatial position of the brimsof blades for the propeller of the invention are mainly determined bycalculation and testing evaluation, through the synthetic considerationin terms of various requirements such as for the fluid sucking, decreaseof the induced drag, minimization of the friction drag and form drag,and the structural strength. These depend on the specific requirementsin use. If the propeller is used to produce thrust and thereby theminimum loss of induced drag is needed, then the brims are provided onboth positive and negative-pressure faces and relatively high. If thepropeller is used as a fan and thereby the loss of induced drag onnegative-pressure face of the blades is not needed to reduced, then nobrims are provided on the negative-pressure faces (see FIG. 4). Theshape, size, spatial angle and spatial position of the brims of bladesfor the propeller of the invention depend on the conditions in use suchas the effective angle of attack, the loading intensity, the pitch, theaspect ratio, the radius, and the linear velocity at the tip for theblades, the compression coefficient, the density, and the viscosity offluid, and the deferential pressure between the inflow and outflow, thedeferential pressure between the inflow or outflow and surroundingatmosphere, etc.

[0063] At the tip of blades, the radial component of the fluid movementis big, the brims of blades give the effect on suppressing both theinduced drag and the fluid supplement in radial direction for thepropeller. Therefore, The shape, size, spatial angle and spatialposition of the brims of blades all influence the acting results.

[0064] The brims of blades for the propeller of the invention can havean inclination relative to the axial direction of the propeller (seeFIG. 4). The brim on the positive-pressure face of blade may producefour utilizable effects when the inclination of brim changes: (1) if thebrim with outward inclination has a radial velocity component acting onfluid being less than the radial velocity of fluid movement, then fluidproduces an acting force on the brim including the component that pushesthe propeller to rotate and the component that decreases the bendingafterward deformation of blade. Under this circumstance, the brim onlyhas a friction drag and no form drag, and increases the inflow amount offluid owing to outward inclination of brim; (2) if the brim with outwardinclination has a radial velocity component acting on fluid being equalto the radial velocity of fluid movement, then the brim produces noacting force on fluid. The brim has also no form drag and increases theinflow amount of fluid owing to outward inclination of brim; (3) if thebrim with outward inclination has a radial velocity component acting onfluid being bigger than the radial velocity of fluid movement, then thebrim produces a radial acting force on fluid. The brim can furtherincrease the sucking amount of fluid but consumes the energy, and hasalso a form drag loss; (4) if the brim on the positive-pressure face ofblade inclines inward, then the brim improves the effect on preventingfluid from overflow, but the inflow amount of fluid decreases, and acertain induced drag is produced on the outward side of brim. The inwardinclination of brim is generally used in conjunction with the outwardinclination of brim such as the outward inclination at lower portion ofbrim and the inward inclination at upper portion near the top edge andotherwise used in special situation such as in helical form. The effectof outward inclination of brim on decreasing of induced drag will bechanged from maximum to zero when the outward inclination of brimchanges from 0 deg. to 90 deg.

[0065] According to the theoretical analysis and testing evaluation, theeffect of propeller technique of the invention on energy saving will berelatively obvious when used in the condition of small aspect ratio ofblade such as less than two. The effect of the brim is relativelyobvious if the inclination of brim, namely the angle included betweenthe brim and the axial direction of the propeller of the invention isless than 45 deg.

[0066] For the blade with relatively small aspect ratio, the fluid mayoverflow beyond the brim to produce induced drag under the actions ofcentrifugal force and blade pressure when the action of the centrifugalforce is strong. If the height of the brim is raised, then the brim maybe so high as to impede supplement of fluid. Under this circumstance, ananti-overflow edge 6 (FIG. 3) can be used to reduce the overflow loss offluid. The anti-overflow edge can be only used for a part of brims nearthe outflow of blades. The result from the use of anti-overflow edge issuccessful for axial conveying of fluid in helical form, such as in asmoke exhauster which has both axial action and centrifugal action.

[0067] The brims in the propeller of the invention can have differentinclination. For example, the outward inclination of brim is bigger atthe portion of blade with less pressure and is less at the portion ofblade with bigger pressure. Similarly, the height of the brims can bechanged according to the needs in different portions.

[0068] The angle of inclination of brim on the negative-pressure face ofblade can be same as that of brim on the positive-pressure face butinward or different therefrom such as the angle constantly parallel toaxial direction of the propeller. The brim on the negative-pressure facegenerally does not incline outward except for special requirement. Thebrim inclining inward means that the brim inclines toward the axialdirection.

[0069] The double-side are brim 1 is generally used to propeller in thetype of propelling. The outward side of the brim along the flow path isadapted to be in streamline form. It can increase the supplement amountof fluid, decrease the interference between the adjacent blades,increase the thrust and consequently improve the performance of thepropeller.

[0070] The single-side arc brim 5 is generally used to propeller in thetype of fan. When the brim has outward inclination relative to axialdirection of propeller, the streamline arc shape or other shape with lowdrag along the flow path is adapted to be used in vicinity of thejuncture between the outer side of brim and the negative-pressure faceof the blade (see FIG. 3). It can further decrease the differentialpressure between the negative and positive-pressure faces, reduce thepressure resistance of the brim, increase the supplement amount offluid, and reduce the energy consumption. In use for relatively highReynolds number, a vortex-generated zone 7 (see FIG. 4) which issubstantially parallel to the negative-pressure face of blade and enableto transfer the flow condition into turbulence should be provided beforethe arc surface. The vortex-generated zone is located at a certain widthof or full surface of brim which is treated as a rough surface or such ashape enabling to transfer the flow condition into turbulance so as todelay the fluid separation and thereby decrease the drag of blades.

[0071] In use for relatively high loading intensity and requirement forhigh structural strength, the propeller of the invention is adapted tobe provided with a strengthening ring 4 (see FIGS. 2,5) to joint theadjacent blades or brims together. Between the adjacent blades there maybe provided with one or several strengthening rings suitably located atthe middle of or end of the blade length. This construction can improvethe structural strength and loading capacity of the propeller anddiminish the flutter of blades. The strengthening ring (see FIG. 5) orthe part thereof can be provided beyond the axial width of blades so asto lessen the obstruction of the strengthening ring to radial sucking offluid. The strengthening ring also serves to control the flow directionlike a tunnel.

[0072] The construction that the blade is connected with the brim at anangle for propeller of the invention can improve the resistance againstdeformation.

[0073] The brim, strengthening ring and anti-overflow edge for thepropeller of the invention will be in the various shapes of curvedfaces, cross-sections or a cross-section with a hollow core.

[0074] The application scope for the propeller of the invention mainlyrefers to the vane-wheel machinery which make the work on fluid, such aspropeller, fan, axial flow blower, compressor, axial flow smokeexhauster and so on.

1. A high-performance propeller having one hub (2) and a plurality ofblades (3), characterized in that there is a double-side arc brim (1) orsingle-side arc brim (5) on the tip of each blade.
 2. A propelleraccording to claim 1, characterized in that said double-side arc brim(1) or single-side arc brim (5) has an inclination relative to axialdirection of the propeller.
 3. A propeller according to claim 1,characterized in that there is a strengthening ring (4) among said blade(3).
 4. A propeller according to claim 1, characterized in that theaspect ratio of said blade (3) is less than 2, and the propeller isconfigured in helical form.
 5. A propeller as recited in claim 1, ischaracterized in that the juncture between the brim and thenegative-pressure face of the blade for said single-side arc brim (5)has a relatively smooth arc surface, or a streamline or approximatelystreamline arc surface along the flow direction, or a vortex-generatedzone (7) on or before the arc surface.
 6. A propeller according to claim1, characterized in that said double-side arc brim (1) or single-sidearc brim (5) has an anti-overflow edge (6).
 7. A propeller according toclaim 1, characterized in that the angle included between saidsingle-side arc brim (5) or double-side arc brim (1) and the axialdirection of propeller is less than 45 deg.